Not Applicable
(1) Field of the Invention
The present invention relates to a method and apparatus for conveying, feeding and positioning parts to workpieces. In general, the parts are to be welded onto the workpieces. The method and apparatus includes a vibratory bin for orientating the parts, a conveyance and feed system for conveying and feeding the parts one at a time to a positioning cylinder which moves the individual parts to the workpieces. The vibratory bowl moves the parts into a row and uses a gauge to ensure that the parts have the correct orientation. The conveyance and feed system moves the parts from the bowl to the positioning cylinder, separates the parts and holds the parts to ensure that the individual parts are fed at a predetermined rate to the positioning cylinder. The positioning cylinder moves each separate part to each workpiece and deposits the part on the workpiece. The positioning cylinder uses magnetism to hold the parts during movement of the parts toward the workpieces. The positioning cylinder then uses the forward inertia of the parts to deposit the parts on the workpieces.
(2) Description of the Related Art
The related art has shown various types of positioning apparatus for positioning parts on workpieces. Illustrative are U.S. Pat. No. 2,623,974 to Prucha; U.S. Pat. No. 3,293,402 to Graham; U.S. Pat. No. 4,020,316 to Schaft et al; U.S. Pat. No. 4,609,805 to Tobita et al; U.S. Pat. No. 4,754,116 to Naruse et al; U.S. Pat. No. 4,789,768 to Tobita et al; U.S. Pat. No. 5,359,171 to Aoyama and U.S. Pat. No. 5,688,414 to Kondo.
In particular, Kondo describes a stud welding apparatus which uses an electromagnet to pull and hold the flanged stud in the collet. The stud is also held in the collet by the gripping force of a resilient gripper located in the bore of the collet. The apparatus uses a pneumatic piston to move the collet with the stud toward the panel to which the stud is to be mounted.
In addition, Naruse et al describes a projection welder for welding a nut to one side of a work. The welder includes a parts feeder connected by a flexible feeder tube to a feeder head which feeds nuts to the lower electrode of the welder. When the preceding operation has been completed and the upper electrode has been lifted, a signal to the succeeding nut is emitted. Simultaneously, the electromagnetic coil is energized to magnetize the push rod so that the shoulder surface at the front end portion of the push rod is also magnetized. The cylinder is activated to move the piston rod, the connector and the push rod forward which moves the front end portion of the push rod into the lower part of the chute through an opening. Thus, the nut turning portion at the front end portion of the push rod is inserted into the threaded hole in the lowermost nut in the chute and the shoulder surface on the push rod is brought into abutment engagement with the lowermost nut whereby the nut is magnetically held on the nut turning portion.
The forward movement of the piston rod is continued and the lowermost nut is removed from the chute. When the push rod has been moved to a position in which the front face of the nut is close to the nut centering pin on the lower electrode, a sensor is operated to de-energize the electromagnetic coil so that the push rod is demagnetized. However, the nut is held on the front end portion of the push rod due to the inertia produced by the thrust force of the shoulder surface. The forward movement of the push rod is further continued to bring the front face of the lower part of the nut on the rod into engagement with the nut centering pin so that the movement of the nut is now blocked by the pin. Further movement of the push rod moves the upper part of the nut so that the nut is rotated counterclockwise over an angle of about 90 degrees about the lower part thereof until the nut is placed on the top face of the electrode tip with the threaded hole in the nut receiving the nut centering pin. Thus, the nut makes contact with the lower electrode and is rotated off the end of the rod.
The related art has also shown several different types of vibrating bowls for use with feed and conveyance machines. Illustrative are U.S. Pat. No. 3,115,239 to Wright; U.S. Pat. No. 3,456,424 to Thurston et al; U.S. Pat. No. 3,457,693 to Jackson; U.S. Pat. No. 3,838,770 to Caffa; U.S. Pat. No. 4,266,653 to Mergl; U.S. Pat. No. 4,629,054 to Kondo; U.S. Pat. No. 4,633,995 to Hamada and U.S. Pat. No. 4,878,575 to McDonald et al.
In particular, Hamada shows a parts feeder having a vibrating bowl. The bowl has a helical parts feeding track extending from the center of the inner bottom of the bowl helically up to a parts outlet in an upper peripheral wall of the bowl.
Further, Caffa shows a vibrating bowl which has a spiral track mounted on the inside. The bowl can have auxiliary devices fitted on any point of the inner wall of the container. The devices may be orientating means, overflows, level indicators, sensors, selectors, orientating and selector devices, automatic column breakers, gauges, counters, etc. which allow for counting the workpieces, determining the absence or presence of workpieces and keeping account of the features of the workpieces.
Finally, Mergl shows the use of gravity and pressurized air to move workpieces along the chute components of a feed system.
Also of interest is U.S. Pat. No. 5,248,869 to DeBell et al which shows a composite weld nut locating pin.
There remains the need for an apparatus and method for moving parts to workpieces which has a vibratory bowl for orientating the parts, a feed and conveyance system for moving the individual parts at a predetermined rate from the bowl and a positioning cylinder which holds each individual part using magnetism and which deposits the part on the workpiece using the forward inertia of the part.
The present invention is a method and apparatus for conveying, feeding and positioning correctly orientated parts to workpieces. The method and apparatus uses a vibratory bowl to arrange the parts in a single file row. The bowl has a gauge which removes parts having the incorrect orientation from the row. It is important to correctly orient the parts to ensure correct operation of the remainder of the apparatus and to ensure that the parts are positioned on the workpieces with the correct orientation. The vibratory bowl allows for quick and accurate sorting and orientating of the parts. The parts move from the bowl into a conveyance and feed system. The conveyance and feed system moves the parts from the bowl to the positioning cylinder and ensures that the parts are fed at correct intervals at the positioning cylinder. The conveyance and feed system uses an escapement to separate and feed the individual parts. The escapement uses a series of pneumatic pistons to hold the parts and block the path of the parts to prevent the parts from randomly moving to the positioning cylinder. The positioning cylinder moves the parts from the conveyance and feed system to the workpieces and deposits the parts on the workpieces. The positioning cylinder uses magnetic attraction between the parts and a portion of the piston rod of the positioning cylinder to hold the parts on the piston rod. The magnetic attraction enables the positioning cylinder to move the parts to the workpieces at any angle without fear that gravity will act to move the parts off the piston rod. The strength of the magnetic attraction is such that the parts will move off the piston rod due to the forward inertia of the parts when the positioning rod stops moving forward.